The present disclosure relates generally to control valves for use in freight car brake equipment, and more particularly to a valve that maintains the brake cylinder pressure in such control valves.
Control valves used in freight car brake equipment (e.g., the DB-60 control valve manufactured by New York Air Brake Corporation, Watertown, N.Y. USA or the ABDX control valve manufactured by Wabtec Corporation, Wilmerding, Pa. USA) are well known. If such control valves supply air pressure to the brake cylinder of a freight car, and the plumbing between the control valve and the freight car has a leak, then the brake cylinder will not maintain the original set pressure. This could be due to, for example, a leaking packing cup in the brake cylinder, a leaking hose, or any other reason that would lead to the leaking of pressure between the connection of the control valve and the brake cylinder.
One means of avoiding such problems may be to have a valve that maintains the brake cylinder pressure. When the pressure in the brake cylinder drops below its original set pressure, such a maintaining valve may feed brake pipe (BP) pressure through a choke to replenish and maintain brake cylinder (BC) pressure up to a certain point. If the leak is too great (i.e., to the extent it exceeds the capacity of the choke), the brake cylinder will not be maintained. Such a maintaining valve may be either integrated into the control valve, or it may be mounted remotely to the brake system. If mounted remotely, it may be connected by multiple ways, including through a conventional 4-port access plate.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.